Serial ATA (SATA) Interfaces are used as interfaces between a peripheral device such as a hard disk drive and a host such as a personal computer. SATA interface is primarily designed for transfer of data between such a host and attached device.
In attempting to better manage power consumption and power savings in SATA, SATA power management is typically handled by three interface power states. The three SATA interface power states are: PhyReady, Partial, and Slumber.
In PhyReady state the interface is synchronized and capable of receiving and sending data. In Partial and Slumber states are the two power saving modes. In both Partial and Slumber states, the interface is not in condition for any active receiving and sending of data. The difference between Partial and Slumber states is mainly in the time required for them to be restored to PhyReady state. SATA standards stipulate that time required to restore from a Partial state to a PhyReady state be no more than 10 us while the time required to restore from a Slumber state to PhyReady state is no more than 10 ms.
These interface power states maybe initiated either by the Host or the Device and are often referred to as Host Initiated Power Management (HIPM) or Device Initiated Power Management (DIPM). The interface power states can further be associated with the Device power management states. In both HIPM and DIPM, what triggers a switch of a power saving mode to the Partial and Slumber interface power state is the lack of activity or data transfer in the interface when the interface is in a PhyReady state.
HIPM and DIPM are not direct user managed methods for power management on the interface and the switching to power savings modes are dependent on a lack of activity on the SATA interface. In addition, once in the power saving modes, no data transfer occurs on the interface until the interface is switched back to the PhyReady State.